A data communication network may include multiple talkers (or sources of data) and multiple receivers. Any number of bridges may be connected in a daisy chain between each of the talkers and the receivers. The data communication network may be an arbitrary network (referred to as a non-engineered network) or non-arbitrary network (referred to as an engineered network). An arbitrary network may be, for example, a residential local area network (LAN), which may have different network devices (e.g., computers, cellular phones, televisions, printers, and electronic tablets) arbitrarily connecting and disconnecting at various points in the network and at random times. The network devices may connect and disconnect at any time regardless of the priority levels of data being transmitted in the arbitrary network.
A non-arbitrary network may be, for example, an automotive network within a vehicle or a manufacturing assembly line network. In general, network devices in a non-arbitrary network are fixed and are not being connected and/or disconnected from the non-arbitrary network. Although network devices may be connected to and/or disconnected from a non-arbitrary network, communication with a network device that is being connected to or disconnected from the non-arbitrary network is prevented during transmission periods of high-priority data. During these transmission periods, high-priority data is transmitted between network devices in the non-arbitrary network.
For example, a non-arbitrary Ethernet network that is operating according to Institute of Electrical and Electronics Engineers (IEEE) 802.1BA may include a talker (or source), multiple bridges and a listener (or receiver). The talker may transmit high-priority data to the listener over the bridges during allocated transmission periods of periodic transmission time intervals. High-priority data may refer to, for example, Class A or Class B data with low-latency requirements. The term latency refers to time for a frame to be transmitted through one or more hops of the non-arbitrary network. The latency of a single hop is measured from a time when a last bit of a frame is received by a network device for that hop to a time when the last bit is transmitted from the network device. For store-and-forward methods, the latency of a single hop is measured from the last bit into the network device to the last bit out of the network device. For cut-through methods, the latency is measured from the first bit into the network device to the first bit out of the network device. A single hop may refer to a talker (referred to as an end station) or a bridge of the non-arbitrary network.
In a non-arbitrary network, transmitted data may have, for example, one of three priority levels. Class A data may include audio video bridging (AVB) data with a highest priority level. Although AVB data may include audio data and/or video data, AVB data may also include control data, user data, reference data, or other types of data. The highest priority level data may be provided with a predetermined amount of bandwidth and a predetermined maximum latency. This assures that the Class A data is transmitted during allocated time periods and latency associated with transmitting the Class A data over a predetermined number of hop(s) and/or between end stations is less than the predetermined maximum latency. Class B data may be AVB data with a next highest priority level. Non-AVB data may have a lowest priority level. In general, higher priority data is transmitted before lower priority data.
IEEE 802.1 Qbv is a specification for a time aware shaper in the AVB generation 2 network and is referred to as time sensitive networking (TSN). Network devices operating according to IEEE 802.1 Qbv may connect to a network at any time. However, the communication and/or use of the network by the network devices may be restricted such that high priority data is permitted to pass through the network ahead of the communication and/or use by the network devices.
Fast Ethernet (FE) refers to transmitting data at 100 mega-bits per second (Mbits/s). Gigabyte Ethernet (GE) refers to transmitting one giga-bit per second (Gbits/s). According to IEEE 802.1 AVB standards for a generation 1 Ethernet network (at FE or GE transmission speeds), a Class A frame of data is to pass through seven hops in less than 2 milli-seconds (ms) and a Class B frame of data is to pass through seven hops in less than 50 ms. According to IEEE 802.1 AVB goal 1 for a generation 2 network a Class A frame is to pass through 32 GE transmission speed hops in less than 125 μs. Time to transmit data over wireless connections is longer than time to transmit data over wired connections.